This invention relates to improved fuse holders and more particularly to fuse clips for use in fuse holders adapted for retaining fuses having ferrule terminals.
Fuses in electrical circuits are designed to provide protection in the event of an overcurrent in the circuits resulting from an unintended lowering of the circuit impedance. Under normal operation the fuse and its associated holder should present a relatively small impedance so that the voltage drop across the fuse and its holder is minimal and has effectively no influence on the circuit being protected. Furthermore, the heat buildup in the fuse and its associated holder must be minimized.
Conventional fuse holders and their associated fuse clips generally include terminal tangs extending from the fuse clips for connection to wires of the circuit to be protected. Examples of these prior art fuse holder designs are disclosed in U.S. Pat. No. 737,407 to Downes, U.S. Pat. No. 2,740,735 to Swain, and U.S. Pat. No. 3,419,839 to Matthews. These patents disclose attaching the clips to mounting members by means of screws or rivets. Other mounting means for conventional fuse clips are disclosed in U.S. Pat. No. 2,229,989 to Roby, U.S. Pat. No. 2,738,486 to Woodsworth, U.S. Pat. No. 2,783,331 to Sundt, U.S. Pat. No. 2,942,228 to Swick, and U.S. Pat. No. 3,492,628 to Matthews. In these, crimped connections of the clip to the mounting member are disclosed. The disadvantage of these prior art fuse holders is that the terminal tang increases the space required for mounting the fuse clip and adds to the impedance of the fuse holder.
U.S. Pat. No. 1,204,691 to Sachs, though not using a tang to provide a connection to the fuse clip, teaches a fuse clip mounted by means of a threaded grommet to a mounting block and having the wire connection made in the interior of the fuse clip by means of a clamp plate secured by a screw in the threaded grommet. The grommet is fitted to the mounting block through an opening in the block. The clip is mounted on the upper end of the grommet by means of an opening in the base of the clip. The upper end of the grommet is expanded to slip over the opening in the clip thereby securing the clip to the block.
U.S. Pat. No. 1,902,804 to LaMar discloses a fuse clip having a wire connection interior to the clip. The clip is mounted to the base by means of a bolt through the base and is secured by a nut. Connection of a wire is provided by means of a second nut on the bolt. Conduction from the circuit to the fuse clip is not direct, but is through a series of mechanical connections which serve to increase the contact impedance presented by the fuse holder to the protected circuit.
U.S. Pat. No. 2,435,794 to Niccolazzo discloses a fuse clip mounted by means of a screw and nut to a mounting block. The wire connection to the interior of the fuse clip is by means of the same screw and nut whereby the clip is loosened from the mount whenever a wire is removed or is connected. No means is provided to prevent rotation of the clip during insertion or removal of a wire.
British Pat. No. 203,427 (1923) to Wootton discloses a clip for block-type fuses having a one-piece fuse clip comprising a pair of retaining arms and a stem extending from the retaining arms and terminating in a circuit member. The associated mounting block contains an opening to receive the stem and circuit member. A screw through the bottom of the circuit member entering through an opening in the bottom of the mounting block is provided to secure a wire connection interior to the circuit member. A similar arrangement is disclosed in U.S. Pat. No. 3,538,492 to Genovese. Both the Wootton (British) and Genovese patents require access to both the top and the bottom of the clip to insert or remove connections.
British Pat. No. 750,332 (1956) to Young discloses a clip having convex side arms for retaining a fuse and a pair of stems extending away from the main body and terminating in a circular member. The fuse block is formed such that mounting of the fuse clip is provided by a circular opening in the block, the opening having a channel to accept the stem. A threaded opening is provided in the side wall of the block to align with an opening in the side of the circular member, and a wire connection inserted into the circular member is secured by a screw through the side. Inserting and removing a fuse is accomplished from the top of the fuse clip whereas inserting and removing a wire requires access to the side of the fuse clip.